Prevent WP update checking

functions.php

// Tell WP everything is up to date
add_filter( 'pre_site_transient_update_core', 'le_prevent_update_checks' );
add_filter( 'pre_site_transient_update_plugins', 'le_prevent_update_checks' );
add_filter( 'pre_site_transient_update_themes', 'le_prevent_update_checks' );
function le_prevent_update_checks() {

	global $wp_version;

	return (object) array(
		'last_checked' => time(),
		'version_checked' => $wp_version
	);

}

In my local development projects the WP update checks tend to time out and cause admin screens to load slowly. This prevents update checking, but it does mean you should disable it occasionally to receive updates.